So far, for example, Patent Document 1 discloses a control apparatus for an internal combustion engine. This conventional control apparatus estimates a blow-through amount of fresh air that blows through a combustion chamber from an intake passage to an exhaust passage, on the basis of the concentration of oxygen in the exhaust passage detected by an air fuel ratio sensor. On that basis, a valve overlap period is controlled in accordance with this amount of blow-through of the fresh air.
Including the above described document, the applicant is aware of the following documents as related art of the present invention.